1. Field of the Invention
The present invention relates to an ink composition which has solved the phenomenon of a printed article (color recorded image) differing according to the light source used when viewing the printed article (metamerizm), i.e., the constant colors of the printed article can be held regardless of the light source, and which has reduced the total amount of inks used when the ink composition is simultaneously used with another ink composition.
2. Description of Prior Art
Various recording methods for forming vivid, high-quality color images have been developed in the past. In particular, an ink jet recording method forms a high-quality image through an ink jet output using an ink set including a plurality of color ink compositions such as a yellow ink, a magenta ink, a cyan ink and a black ink.
However, with these previously proposed ink sets, a printed article (color recorded image) produced by printing on a recording medium such as paper differs in color according to differences in the light source (fluorescent lamp, incandescent lamp, sunlight etc.). That is, a phenomenon (metamerism) occurs in which the colors of a printed article when viewed using one light source are different when viewed using another light source. In general, metamerism refers to the phenomenon in which two colors having different spectral distributions appear to be the same color under certain illumination conditions or the like, but appear to be different colors when the illumination conditions or the like, are changed. Here, ‘illumination conditions or the like’ includes not only the illumination conditions themselves, but also the temperature of the light, and the characteristics of the color vision of the viewer. Such metamerism is used in the evaluation of lighting and object colors, but metamerism with industrial products is often a problem in terms of color matching.
In a recording medium, there is a limitation on the total amount of inks which can be fired thereon per unit area (hereinafter this limitation is also referred to as ‘ink duty limitation’). That is, an ink recording on a recording medium, in excess of the amount defined by the ink duty limitation, may cause ink blotting and reduce the image quality pertinent to the recording article obtained. Thus it has been impossible to raise the concentration of formed dots without limitation.
In order to ensure good printing quality, it is necessary, as described above, that the ink firing amount be within the range of the ink duty limitation. However, if the ink firing amount (i.e. the amount of inks used) is limited, the coloring ability and the color reproduction range of a recorded image are necessarily limited and it is difficult to improve the image quality, particularly in a region of low-brightness (shadow region). In order to enhance the color ability or expand the color reproduction range, the active use of an ink with high color concentration can be considered; however, the increase in the use of an ink with a high color concentration generally causes the dots of the discharged inks to be visible in a recording medium, i.e., grainy image, and thus reduced image quality.